Cisco Aironet Problems w/8400

Calling all wireless experts! We / I need your help with a problem we've been having. We buy the Cisco Aironets to use as our APs, and on two jobs we've had terrible luck with them. Routinely, the MVP-8400s in the system would not connect to the APs for the life of them. We'd have to reboot, reboot, reboot and reboot again until it finally would connect, and hours later would fall offline. Once we swapped it out with a basic Linksys AP, everything would be fine. The panel would connect to it immediately and has yet to fall offline. My laptop (Dell Latitude D620) could connect to the same access point and have no troubles whatsoever. The APs do have a 128 WEP encryption, and do broadcast SSID - these two settings are identical on both the Cisco & the Linksys. We typically use channels 1, 6 or 11 and changing them had no effect when the panel couldn't connect. Once we were able to have the panel connect to the Cisco AP, changing the channel on the fly wasn't a problem.

The last time this happened, we armed ourselves with an extra MVP-8400 and an extra Cisco AP. It didn't matter which Cisco was running (of course one at a time) or which panel we had up, neither would connect on the first try. Once we threw in the Linksys - bam, worked like a charm and has not fallen offline since the re-install. Both panels however had the "older" wireless cards that don't do the "Site Survey".

Has anyone had similar if not identical problems? Also, if you use Cisco Aironet APs, what settings do you use? Anything specific that you go in and make certain is changed?